Air intake of an aircraft turbojet engine nacelle comprising ventilation orifices for a de-icing flow of hot air

ABSTRACT

The invention relates to an air intake of an aircraft turbojet engine nacelle, extending along an axis X, in which an air flow circulates from upstream to downstream, the air intake comprising an inner wall facing the axis X and an outer wall for guiding an external air flow, the walls being connected by a leading edge and an inner partition so as to delimit an annular cavity. The air intake comprises means for injecting at least one hot air flow into the inner cavity and at least one ventilation orifice formed in the outer wall to allow the hot air flow to escape after heating the inner cavity, the ventilation orifice comprising an upstream edge, the circumferential profile of which is discontinuous in order to generate turbulences, and a downstream edge, the radial profile of which is aerodynamic in order to limit the formation of pressure fluctuations.

TECHNICAL FIELD

The present invention relates to the field of aircraft turbojet enginesand is more particularly directed to an air intake of an aircraftturbojet engine nacelle comprising a de-icing device.

In a known manner, an aircraft comprises one or more turbojet engines toallow its propulsion by acceleration of an air stream that circulatesfrom upstream to downstream in the turbojet engine.

With reference to FIG. 1, a turbojet engine 100 extending along an axisX and comprising a fan 101 rotatably mounted about axis X in a nacellecomprising an external shell 102 in order to accelerate an air stream Ffrom upstream to downstream is represented. Hereinafter, the termsupstream and downstream are defined with respect to the circulation ofthe air stream F. The nacelle comprises at its upstream end an airintake 200 comprising an internal wall 201 pointing to axis X and anexternal wall 202 which is opposite to the internal wall 201, the walls201, 202 are connected through a leading edge 203 also known as “airintake lip”. Thus, the air intake 200 allows the incoming air stream Fto be separated into an internal air stream INT guided by the internalwall 201 and an external air stream EXT guided by the external wall 202.The walls 201, 202 are connected through the leading edge 203 and aninternal partition wall 205 so as to delimit an annular cavity 204 knownto the person skilled in the art as “D-DUCT”. Hereinafter, the termsinternal and external are defined radially with respect to axis X of theturbojet engine 100.

In a known manner, during the flight of an aircraft, due to temperatureand pressure conditions, ice is likely to accumulate at the leading edge203 and the internal wall 201 of the air intake 200 and form blocks ofice that are likely to be ingested by the turbojet engine 100. Suchingestions have to be avoided in order to improve the life of theturbojet engine 100 and reduce malfunctions.

To eliminate ice accumulation, with reference to FIG. 1, it is known toprovide a de-icing device comprising an injector 206 of a hot air streamFAC into the internal cavity 204. The circulation of such a hot airstream FAC allows, by heat exchange, the internal wall 201, externalwall 202 and lip 203 to be heated and thus ice accumulation which meltsor evaporates as it accumulates to be avoided. In a known manner, withreference to FIGS. 2 and 3, the internal cavity 204 comprisesventilation openings 103 formed in the external wall 202 of the airintake 200 so as to allow discharge of the hot air stream FAC afterheating of the internal cavity 204. As an example, with reference toFIG. 3, each ventilation opening 103 has an elongated, preferablyoblong, shape along the engine axis X.

In practice, acoustic nuisance appears during the circulation of theexternal air stream EXT over the ventilation openings 103, inparticular, hissing and/or resonances. Such acoustic nuisance isincreased when the de-icing device is inactive.

An immediate solution to eliminate this drawback is to provide aventilation duct connecting the internal cavity 204 to ventilationopenings offset from the exterior wall of the air intake. Preferably,such a ventilation duct allows the ventilation openings to be positionedin a zone in which the velocity of the outside air stream EXT is lower,thereby limiting acoustic disturbances. In practice, the addition of aventilation duct increases the overall size and mass of the turbojetengine, which is not desired. In addition, a ventilation duct has thedrawback of ejecting a hot FAC air stream in proximity to heat-sensitivedownstream zones, for example, of composite material.

One of the objects of the present invention is to provide an air intakecomprising ventilation openings formed in the external wall of the airintake and not inducing acoustic nuisance.

Incidentally, a curved guide grille for the hot air stream whenexhausted is known from patent application U.S. Pat. No. 5,257,498, butit has no impact on acoustic nuisance.

Incidentally, different ventilation openings are known in prior art frompatent applications EP0921293A1, FR2772341A1 and US201/001003A1.

SUMMARY

The invention relates to an air intake of an aircraft turbojet enginenacelle extending along an axis X in which an air stream circulates fromupstream to downstream, the air intake extending circumferentially aboutaxis X and comprising an internal wall pointing to axis X to guide aninternal air stream INT and an external wall, which is opposite to theinternal wall for guiding an external air stream EXT, the walls beingconnected through a leading edge and an internal partition wall so as todelimit an annular cavity, the air intake comprising means for injectingat least one hot air stream FAC into the internal cavity and at leastone ventilation opening formed in the external wall to allow exhaust ofthe hot air stream FAC after heating the internal cavity.

The invention is remarkable in that it comprises at least one member fordisturbing the external air stream EXT, positioned upstream of theventilation opening, which extends projecting outwardly from theexternal wall. Advantageously, such a disturbance member allowsformation of sound pressure fluctuations to be avoided in the vicinityof the ventilation opening.

Preferably, the disturbance member has a width at least equal to halfthe width of the ventilation opening, more preferably to the width ofthe ventilation opening.

According to one aspect, the distance between the disturbance member andthe ventilation opening is between 0.5 and 3 times the length of thedisturbance member. By distance between the disturbance member and theventilation opening, it is meant the minimum distance between thedisturbance member and the ventilation opening, that is, that connectingthe downstream end of the disturbance member to the upstream end of theventilation opening as illustrated in FIG. 6.

According to another aspect, the distance between the disturbance memberand the ventilation opening is less than 2 times the length of theventilation opening.

According to another aspect, the disturbance member has a height between0.2 and 1 time the length of the disturbance member.

Preferably, the disturbance member is mounted as an insert to theexternal wall.

According to one aspect, the external wall comprises a through openingfor mounting that is positioned upstream of the ventilation opening. Thedisturbance member extends through the through opening for mounting,preferably from within the internal cavity.

According to one aspect, the disturbance member is a deflection memberthat comprises a domed external surface, preferably, with a profilehaving an elliptical portion. This advantageously allows external air tobe deflected not to interact at high velocity with the ventilationopening.

According to another aspect, the disturbance member is a vortexgenerating member. The formation of vortices, that is, turbulentaerodynamic structures, allows formation of acoustic waves to beavoided. In particular, the acoustic nuisance is low when the dimensionsof the turbulent aerodynamic structures are far from those of aventilation opening.

Preferably, the vortex generating member is polyhedral, preferablytetrahedral or pyramidal.

Preferably, the vortex generating member has a convex shape.

Preferably, the vortex generating member comprises a plurality ofprojecting ridges.

The invention relates to an air intake of an aircraft turbojet enginenacelle extending along an axis X in which an air stream circulates fromupstream to downstream, the air intake extending circumferentially aboutaxis X and comprising an internal wall pointing to axis X to guide aninternal air stream INT and an external wall, which is opposite to theinternal wall to guide an external air stream EXT, the walls beingconnected through a leading edge and an internal partition wall so as todelimit an annular cavity, the air intake comprising means for injectingat least one hot air stream FAC into the internal cavity and at leastone ventilation opening formed in the external wall to allow exhaust ofthe hot air stream FAC after heating the internal cavity.

The invention is remarkable in that the ventilation opening comprises anupstream edge whose circumferential profile is discontinuous to generateturbulence and/or a downstream edge whose radial profile is aerodynamicto limit formation of pressure fluctuations.

Advantageously, the turbulent aerodynamic structures formed by theupstream edge make it possible not to interact with the ventilationopening so as not to generate acoustic waves. Advantageously, theaerodynamic radial profile of the downstream edge allows the flow of theexternal air stream to be modified in order to avoid any hissingphenomenon.

According to one aspect, the circumferential profile of the upstreamedge has at least one point of curvature discontinuity in the vicinityof which the direction of the tangent of the profile is modified by anangle greater than 60°, preferably less than 180°.

Preferably, the upstream edge comprises between 1 and 8 points ofcurvature discontinuity for turbulence generation.

Preferably, the upstream edge comprises at least two turbulencegeneration patterns, preferably at least four.

Preferably, the turbulence generation pattern has a scallop or chevronshape.

According to one aspect, the upstream edge is inscribed within theaerodynamic lines of the external wall.

According to another aspect, the upstream edge comprises an outwardlyprojecting portion.

Preferably, the projecting portion forms an angle with the overall planeof the ventilation opening that is less than 45°.

Preferably, the downstream edge has a rounded, preferably domed, radialprofile.

According to one aspect, the ventilation opening defines an aerodynamicline as an extension of the external surface of the external wall of theair intake. The downstream edge is positioned internally to theaerodynamic line.

According to one aspect, the external wall comprising a through openingfor assembling, the ventilation opening is formed in a ventilationmember mounted in the through opening for assembling, preferably frominside.

The invention relates to an air intake of an aircraft turbojet enginenacelle extending along an axis X in which an air stream circulates fromupstream to downstream, the air intake extending circumferentially aboutaxis X and comprising an internal wall pointing to axis X to guide aninternal air stream INT and an external wall, which is opposite to theinternal wall, to guide an external air stream EXT, the walls beingconnected through a leading edge and an internal partition wall so as todelimit an annular cavity, the air intake comprising means for injectingat least one hot air stream FAC into the internal cavity and at leastone ventilation opening formed in the external wall to allow exhaust ofthe hot air stream FAC after heating the internal cavity.

The invention is remarkable in that it comprises at least one acousticmember positioned in the internal cavity facing the ventilation openingso as to modify acoustic resonance frequencies and/or attenuate acousticwaves formed in the internal cavity via the ventilation opening.

Such an acoustic member makes it possible to modify resonancefrequencies or attenuate acoustic waves so as to limit acoustic nuisancelikely to bother local residents. The effects of acoustic nuisance arethus reduced.

Preferably, with the ventilation opening comprising a normal axis, theacoustic member comprises at least one acoustic surface extendingsubstantially orthogonal to the normal of the ventilation opening.

Preferably, the projection of the acoustic surface onto the plane of theventilation opening along the normal axis is larger than the ventilationopening.

According to one aspect, with the ventilation opening comprising anormal axis, the acoustic surface being spaced from the ventilationopening along the normal axis by a spacing distance, the spacingdistance is greater than the length of the ventilation opening.

According to another aspect, with the ventilation opening comprising anormal axis, the acoustic surface being spaced from the ventilationopening along the normal axis by a spacing distance, the spacingdistance is less than twice the length of the ventilation opening.

According to one aspect, the acoustic member comprises at least oneabsorption material to form an acoustic absorption surface.

According to one aspect, the acoustic member is in the form of a cornerpiece comprising an acoustic treatment surface and a mounting surface.

According to one aspect, the acoustic member is attached to the internalsurface of the external wall.

According to one aspect, the acoustic member is attached to the internalwall of the internal cavity.

According to one aspect, the internal partition wall comprises a convexupstream face pointing to the ventilation opening.

According to one aspect, the internal partition wall comprises a concaveportion extending substantially orthogonal to the normal of theventilation opening.

By virtue of the invention, sources and effects of the acoustic nuisancerelating to the ventilation openings are treated alternatively orsimultaneously in order to improve the comfort to the users located inthe aircraft but also that of the local residents. Advantageously, theinvention makes it possible to integrate into a high-temperature thermalenvironment (circulation of the hot flow) without impacting thedischarge flow rate and/or increasing the aerodynamic drag.

The invention can be implemented in a practical manner to act on theacoustic frequencies desired to be modified.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood upon reading the followingdescription, which is given only by way of example, and referring to theappended drawings given as non-limiting examples, in which identicalreferences are given to similar objects and in which:

FIG. 1 is a schematic representation of an axial cross-section view of aturbojet engine according to prior art;

FIG. 2 is a schematic representation of a cross-section view of an airintake according to prior art in which a hot air stream for de-icingcirculates;

FIG. 3 is a schematic perspective representation of a plurality ofventilation openings according to prior art;

FIG. 4 is a schematic representation of an axial cross-section view of aturbojet engine according to prior art;

FIG. 5 is a schematic representation in an axial cross-section view ofan air intake comprising an upstream disturbance member;

FIG. 6 is a top schematic representation of an upstream disturbancemember associated with a ventilation opening;

FIG. 7 is a close-up schematic representation of a first type ofmounting of a deflection member;

FIG. 8 is a close-up schematic representation of a second type ofmounting of a deflection member;

FIG. 9 is a schematic representation in an axial cross-section view ofan air intake comprising an upstream vortex generating member;

FIG. 10 is a schematic perspective representation of a first embodimentof an upstream vortex generating member;

FIG. 11 is a schematic perspective representation of a second embodimentof an upstream vortex generating member;

FIG. 12 is a top schematic representation of the perimeter of aventilation opening according to prior art;

FIG. 13A, FIG. 13B, and FIG. 14 are top schematic representations of aventilation opening having an upstream edge with scallops;

FIG. 15A, FIG. 15B, and FIG. 16 are schematic top views of a ventilationopening having an upstream edge with chevrons;

FIG. 17 and FIG. 18 are top schematic representations of a ventilationopening having a raised upstream portion;

FIG. 19 is a schematic longitudinal representation in a cross-sectionview of a ventilation opening according to prior art;

FIGS. 20-23 are schematic representations in a longitudinalcross-section view of ventilation openings according to the inventionwith a downstream edge having an aerodynamic radial profile;

FIG. 24 is a schematic longitudinal representation in a partialcross-section view of a ventilation member mounted as an insert in athrough opening for assembling;

FIG. 25 and FIG. 26 are schematic representations of an acoustic membermounted in the internal cavity to the internal partition wall;

FIG. 27 is a schematic representation of an acoustic member mounted inthe internal cavity to the external wall;

FIG. 28 is a schematic representation of an acoustic member integratedto the internal partition wall;

FIGS. 29-31 are schematic representations of an acoustic membercomprising an absorption material.

It should be noted that the figures set out the invention in detail forimplementing the invention, said figures of course being able to serveto better define the invention if necessary.

DETAILED DESCRIPTION

The invention will be set out with reference to FIG. 4 showing aturbojet engine 1 extending along an axis X and comprising a fan 11mounted rotatably about axis X in a nacelle 2 comprising an externalshell 12 in order to accelerate an air stream F from upstream todownstream. Hereinafter, the terms upstream and downstream are definedwith respect to the circulation of the air stream F. The nacelle 2comprises at its upstream end an air intake 2 comprising an internalwall 21 pointing to axis X and an external wall 22 which is opposite tothe internal wall 21, the walls 21, 22 are connected through a leadingedge 23 also referred to as “air intake lip”. Thus, the air intake 2allows the incoming air stream F to be separated into an internal airstream INT guided by the internal wall 21 and an external air stream EXTguided by the external wall 22. The walls 21, 22 are connected throughthe leading edge 23 and an internal partition wall 25 so as to delimitan annular cavity 24 known to the skilled person as “D-DUCT”.Hereinafter, the terms internal and external are defined radially withrespect to axis X of the turbojet engine 1.

The air intake 2 comprises a de-icing device comprising means forinjecting 26 a hot air stream FAC into the internal cavity 24, forexample, an injector. The circulation of such a hot air stream FACallows, by heat exchange, the internal wall 201, external wall 202 andlip 203 to be heated and thus ice accumulation which melts or evaporatesas it accumulates to be avoided. As illustrated in FIG. 4, the internalcavity 24 comprises one or more ventilation openings 3 formed in theexternal wall 22 of the air intake 2 so as to allow the hot air streamFAC to be discharged after heating the internal cavity 24. In practice,the ventilation openings 3 are positioned upstream of the injector 26relative to the point of injection of the hot air stream FAC into theair intake 2, where upstream is defined in this sentence with respect tothe circumferential circulation of the hot air stream from upstream todownstream in the circumferential air intake 2.

According to one aspect of the invention, with reference to FIGS. 5 and6, the air intake 2 comprises at least one disturbance member 4 for theexternal air stream EXT, positioned upstream of a ventilation opening 3,which extends projecting outwardly from the external wall 22. In otherwords, the disturbance member 4 makes it possible to act on theexcitation causing the acoustic nuisance by reducing its influence.

Hereinafter, the invention is set forth in an orthogonal reference frameP, Q, N in which axis P extends along the external wall from upstream todownstream, axis N extends normally to the ventilation opening 3 frominside to outside and axis Q extends tangentially.

The ventilation opening 3 is defined in the orthogonal reference frameP, Q, N. To this end, the ventilation opening 3 comprises a length P3defined along axis P and a width Q3 defined along axis Q as illustratedin FIG. 6.

In order to be able to optimally influence the upstream external airstream EXT, that is the acoustic excitation, the disturbance member 4has a width Q4 at least equal to half the width Q3 of the ventilationopening 3, preferably to the width Q3 of the ventilation opening 3 asillustrated in FIG. 6. Preferably, the widths Q3, Q4 are of the sameorder of magnitude to limit aerodynamic disturbances. Also, the distanceΔP, defined along axis P, between the disturbance member 4 and theventilation opening 3 is between 0.5 and 3 times the length P4 of thedisturbance member 4. Preferably, the distance ΔP is less than 2 timesthe length P3 of the ventilation opening 3. This advantageously allowsthe external air stream EXT to be disturbed prior to its interactionwith the ventilation opening 3 while limiting drag.

0.5*P4≤ΔP≤3*P4  [Math. 1]

ΔP≤2*P3  [Math. 2]

Even more preferably, as illustrated in FIG. 7, the disturbance member 4has a height N4, defined along axis N, between 0.2 and 1 time the lengthP4 of the disturbance member 4. Such a restricted height allows anacoustic interaction of the external air stream EXT with the ventilationopening 3 to be avoided while limiting aerodynamic disturbances.

According to one aspect of the invention, with reference to FIG. 7, thedisturbance member 4 is of the same material as the external wall 22 orattached as an insert to its external surface 22 a, for example, bybonding, welding or the like. According to another aspect of theinvention, with reference to FIG. 8, the external wall 22 comprises athrough opening 400 for mounting, positioned upstream of the ventilationopening 3. The disturbance member 4 extends through the through opening400 for mounting so as to extend projecting outwardly from the externalwall 22. In the example shown in FIG. 8, the disturbance member 4comprises a mounting base 41 configured to be attached to the internalsurface 22 b of the external wall 22, in particular, by bonding welding,riveting or the like. In other words, the disturbance member 4 can bemounted from outside (FIG. 7) but also from inside (FIG. 8) depending onmounting and overall size restrictions.

Two embodiments of a disturbance member 4 will now be set forth indetail.

In a first embodiment, with reference to FIGS. 5 to 8, the disturbancemember is a deflection member configured to deflect the external airstream EXT in order to prevent it from having a grazing incidence duringits interaction with the ventilation opening 3. The formation ofacoustic pressure fluctuations in the vicinity of the ventilationopening 3 is avoided, thereby reducing acoustic nuisance.

Preferably, the deflection member comprises an external surface 40 thatis domed. Advantageously, this prevents too high a deviation of the flowof the modified external air stream EXTm. Preferably, the externalsurface 40 has a portion of elliptical profile, that is, inscribedwithin an elliptical perimeter along an axial cross-sectional plane (N,P) as illustrated in FIGS. 5, 7 and 8. Such an external surface 40allows to modify stream lines without generating a significant increasein drag. The dynamic flow remains minimally disturbed and is simplydeflected.

In a second embodiment, with reference to FIGS. 9 to 11, the disturbancemember is a vortex generating member 4′ in order to create aerodynamicdisturbances. Vortices are aerodynamic structures with a turbulentcharacter, which prevents the generation of acoustic pressurefluctuations due to the interaction between the external stream EXT andthe ventilation opening 3.

The geometrical dimensions previously set out for the disturbance memberapply to the deflection member and the vortex generating member. Theywill not be detailed again.

As illustrated in FIGS. 9 to 11, the vortex generating member 4′ ispolyhedral, preferably tetrahedral (triangle base) or pyramidal (squarebase). The presence of faces and/or ridges allows generation of vorticesEXTv as illustrated in FIG. 9 in the external air stream EXT along aplurality of different directions in order to generate an external airstream with aerodynamic disturbances.

According to a first aspect, with reference to FIG. 10, the vortexgenerating member 4′ has a convex, preferably solid, shape so as todefine a plurality of deflection faces 41′ which are connected throughprojecting ridges 42′. According to a second aspect, with reference toFIG. 11, the vortex generating member 4′ comprises a plurality ofprojecting ridges 42′ that are connected through concave portions 43′ soas to significantly disturb the external air stream EXT.

A reduction in acoustic nuisance has been set out for a singleventilation opening 3, but it goes without saying that some or all ofthe ventilation openings 3 could be associated with members 4, 4′ fordisturbing the external air stream having identical or differentnatures.

When several disturbance elements 4, 4′ are used together, they can beindependent or connected together, for example, in a continuous mannerbetween two adjacent ventilation openings 3.

Advantageously, such disturbance members 4, 4′ make it possible to acton the cause of the acoustic nuisance, that is, on the external airstream EXT located upstream of the ventilation opening 3 so as to reducegeneration of acoustic pressure fluctuations.

In a conventional manner, with reference to FIG. 12 representing aventilation opening 3 according to prior art, the ventilation opening 3has an oblong shape whose length is defined along axis P extending fromupstream to downstream. The upstream edge 31 and the downstream edge 32have a curvilinear shape so as to limit mechanical fatigue.

According to one aspect of the invention, with reference to FIGS. 12 to18, the ventilation opening 3 comprises an upstream edge 31 whosecircumferential profile is discontinuous to generate turbulence and/or adownstream edge 32 whose radial profile is aerodynamic to limitformation of pressure fluctuations. In other words, the profile of theedge of the ventilation opening 3 is modified so as to limit acousticdisturbances. An irregular upstream edge 31 allows relaxing of smallturbulent aerodynamic structures that do not generate acoustic nuisancewith the ventilation opening 3.

On the one hand, as will be set forth later, the upstream edge 31 cancomprise a discontinuous circumferential profile to generate turbulenceand thus disturb the upstream external air stream in the manner of anupstream disturbance member as set forth previously. In other words, theupstream edge forms a disturbance member integrated to the ventilationopening 3. Thus, the interaction with the ventilation opening 3 iscontrolled.

On the other hand, as will be set forth later, the downstream edge 32can comprise an aerodynamic profile along the radial direction to limitformation of pressure fluctuations. Advantageously, this prevents theoccurrence of hissing. Thus, antagonistic treatments of opposite edges31, 32 of a ventilation opening 3, alternatively or cumulatively, allowsthe generation of acoustic nuisance to be counteracted.

Preferably, the ventilation opening 3 has a ratio of length, definedalong axis P, to width, defined along axis Q, that is between 2 and 5.

According to one aspect of the invention, the profile of the upstreamedge 31 in the circumferential direction has at least one point ofcurvature discontinuity 34 in the vicinity of which the tangent ismodified by an angle ΔT greater than 60°, preferably less than 180°.Preferably, the upstream edge 31 comprises at least two, preferably, atleast four turbulence generating patterns 33. Preferably, the turbulencegenerating patterns 33 are adjacent to each other. The circumferentialprofile is defined in the plane (P, Q).

As illustrated in FIGS. 13A and 13B, there is represented an upstreamedge 31 comprising two scallop-shaped turbulence generating patterns 33so as to define at their interface a point of curvature discontinuity 34that extends projecting to the center of the ventilation opening 3. FIG.13B illustrates the tangent T1 of the first turbulence generatingpattern 33 and the tangent T2 of the second turbulence generatingpattern 33 which are separated by an angle ΔT of between 160° and 180°.Such a point of discontinuity 34 allows the flow of the external airstream EXT to be disturbed before it interacts with the downstream edge32.

According to another embodiment illustrated in FIG. 14, the upstreamedge 31 comprises four scallop-shaped turbulence generating patterns 33and three points of curvature discontinuity 34 that extend projecting tothe center of the ventilation opening 3 in order to generate a largenumber of aerodynamic disturbances.

Similarly, according to another embodiment illustrated in FIGS. 15A and15B, there is represented an upstream edge 31 comprising twochevron-shaped turbulence generation patterns 33′ so as to define aninner point of curvature discontinuity 34′ and a point of curvaturediscontinuity 34′ at the interface with another generation pattern 33′.Also, in this example, the upstream edge 31 comprises 3 points ofcurvature discontinuity 34′, 1 of which extends projecting to the centerof the ventilation opening 3 and 2 of which extend projecting oppositelyto generate a large number of aerodynamic disturbances. Similarly toFIG. 13B, FIG. 15B illustrates the tangent T1′ of the first turbulencegenerating pattern 33′ and the tangent T2′ of the second turbulencegenerating pattern 33′ being spaced apart by an angle ΔT′ between 90°and 110°.

With reference to FIG. 16, the upstream edge 31 comprises fourchevron-shaped turbulence generation patterns 33′ and 7 points ofcurvature discontinuity 34′, 3 of which project toward the center of theventilation aperture 3 and 4 of which extend projecting oppositely inorder to generate a large number of aerodynamic disturbances.

It goes without saying that the number and shape of turbulencegenerating patterns 33, 33′ as well as the number, shape and position ofthe points of curvature discontinuity 34, 34′ can vary as required.Preferably, the upstream edge 31 comprises between 1 and 8 points ofcurvature discontinuity 34, 34′ for vortex generation depending on thedesired acoustic effect.

According to one aspect of the invention, the upstream edge 31 isinscribed in the aerodynamic lines and belongs to the plane (P, Q), thatis, along an aerodynamic line. Such an upstream edge 31 is simple tomake. According to another aspect, the upstream edge 31 comprises anoutwardly projecting portion 35′. As an example, as illustrated in FIGS.17 and 18 representing an upstream edge 31 comprising chevron-shapedturbulence generating patterns 33′, a point of curvature discontinuity34′ extends projecting to the center of the ventilation opening 3 andextends projecting outwardly, that is, above the plane (P, Q) in whichthe ventilation opening 3 extends. In other words, the point ofcurvature discontinuity 34′ makes it possible to generate turbulence inthe manner of an upstream disturbance member 4, 4′ as set forthpreviously by modifying the incidence of the external air stream EXTupstream of the ventilation opening 3. Preferably, the projectingportion 35′ forms an angle θ with the overall plane (P, Q) of theventilation opening 3 that is less than 45°.

Advantageously, the profile of the upstream edge 31 is produced bymechanical cutting, water jet, laser or punching.

In a conventional manner, with reference to FIG. 19 representing aventilation opening 3 according to prior art, the ventilation opening 3comprises a downstream edge 32 having a projecting ridge 320 in theplane (P, Q) of the ventilation opening 3, that is, at the interfacewith the external air stream EXT that sweeps the external wall 22. Thisinterface line, hereinafter referred to as the “aerodynamic line LA”,interacts with the projecting ridge 320 of the downstream edge 32 andgenerates hissing and other acoustic nuisance.

According to one aspect of the invention, as illustrated in FIGS. 20-24,the downstream edge 32 has an aerodynamic profile in the radialdirection to limit formation of pressure fluctuations, that is, to avoidany shearing in the aerodynamic line LA by a projecting ridge. Theradial profile is defined in the plane (P, N).

Preferably, the thickness of the downstream edge 32 is different fromthat of the upstream edge 31. Preferably, the thickness of thedownstream edge 32 is enlarged relative to the upstream edge so as toform an aerodynamic radial profile. Advantageously, the aerodynamicradial profile has a continuous curvature, devoid of discontinuities, inparticular, with respect to the aerodynamic line LA. Advantageously, theaerodynamic radial profile allows for a progressive deflection.

As illustrated in FIG. 20, the downstream edge 32 has an upperaerodynamic, in particular rounded or domed, profile 321 at aerodynamicline LA. In this embodiment, only the upper portion of the downstreamedge 32 is modified.

With reference to FIG. 21, it is suggested to form a fully rounded ordomed downstream edge 32 so as to guide the aerodynamic line LA withoutturbulence both internally or externally thereto. As illustrated inFIGS. 22 and 23, the downstream edge 32 is sloped inwardly of theinternal cavity 24 so as to avoid contact between the external airstream EXT and a projecting ridge. With reference to FIG. 22, thedownstream edge 32 is deformed, in particular, with an inwardly directedprotrusion. With reference to FIG. 23, the downstream edge 32 isdeformed inwardly so as to lie below the aerodynamic line LA.Preferably, the radial profile of the downstream edge 32 can be made bylocal deformation of the material.

According to one aspect of the invention, with reference to FIG. 24, theexternal wall 22 comprises a through opening 305 for mounting and theventilation opening 3 is formed in a ventilation member 300 mounted inthe through opening 305 for assembling, preferably from inside. Such anembodiment is advantageous insofar as it allows a through opening 305for assembling to be formed in a simple shape, without any particularaerodynamic restrictions in the external wall 22. Each ventilationmember 300 can be manufactured independently and advantageously compriseupstream 31 and downstream 32 edges that are worked to reduce acousticdisturbances. Each ventilation member 300 can then be attached as aninsert to a through opening 305 for assembling, in particular, at itsupstream end 301 and downstream end 302 as illustrated in FIG. 24. Suchan embodiment combines improved acoustic performance and ease ofindustrialization.

Modification of an upstream edge 31 and/or a downstream edge 32 of aventilation opening 3 allows for the formation of a ventilation opening3 with reduced acoustic impact.

A reduction in acoustic impact for a single ventilation opening 3 hasbeen set forth, but it is understood that some or all of the ventilationopenings 3 could comprise an upstream edge 31 and/or downstream edge 32modified according to the invention.

According to one aspect of the invention, with reference to FIGS. 25-31,the air intake 2 comprises at least one acoustic member 5 mounted in theinternal cavity 24 facing the ventilation opening 3. By facing theventilation opening, it is meant that the acoustic member 5 is distantfrom the ventilation opening 3 so as not to disturb exhaust of the hotair stream FAC but aligned with the latter to allow treatment of theacoustic waves coming from said ventilation opening 3.

Thus, unlike a treatment of the acoustic excitation as taught in thefirst part, it is suggested here to treat the acoustic resonance as suchby shifting frequencies off the resonant zones or even by attenuatingacoustic waves. The sound amplification of acoustic nuisance isadvantageously reduced.

As illustrated in FIGS. 25 and 26, according to a first embodiment, theacoustic member 5 comprises an acoustic surface 50 extending in front ofthe ventilation opening 3. Here, the acoustic surface 50 issubstantially planar to improve its efficiency but it could also becurved. Advantageously, the acoustic surface 50 is acousticallyreflective so as to modify acoustic wavelengths and thus reduceresonances. Preferably, the treatment surface 50 is made of a metal orceramic material in order to have good high temperature resistance.

As illustrated in FIG. 25, the ventilation opening 3 comprises a normalaxis N and the projection of the acoustic member 5, the acoustic surface50, onto the plane (P, Q) of the ventilation opening 3 along the normalaxis N is larger than the ventilation opening 3 in order to allowcontaining all of the acoustic waves entering through the ventilationopening 3. Preferably, the acoustic surface 50 is substantially parallelto the plane (P, Q) of the ventilation opening 3. In other words, theacoustic surface 50 extends substantially orthogonal to the normal N ofthe ventilation opening 3. According to a preferred aspect, asillustrated in FIG. 26, the acoustic surface 50 comprises at itscircumferential end a curved edge 53 so as to further allow guidingexhaust of the hot air stream FAC towards the ventilation opening 3.

In order to achieve optimal acoustic performance, with reference to FIG.25, the acoustic member 5 is spaced from the ventilation opening 3 alongthe normal axis by a spacing distance N5 which is preferably less than20 mm. This ensures optimal hot air exhaust as well as a shift of theacoustic frequencies into a frequency range that is less disturbing tothe human ear.

In the embodiment of in FIGS. 25 and 26, the acoustic member 5 is in theform of a corner piece defining an acoustic surface 50 and a mountingsurface 51. Preferably, the corner piece has an L-shaped cross-section.Such a simple structure allows for acoustic efficiency withoutsignificantly increasing mass. As illustrated in FIG. 25, the acousticmember 5 can be attached via its mounting surface 51 to the internalpartition wall 25 of the internal cavity 24 (FIG. 25) or to the internalsurface 22 b of the external wall 22 (FIG. 27) so that the acousticsurface 50 extends into the immediate vicinity of the ventilationopening 3.

According to another aspect of the invention, with reference to FIG. 28,the internal partition wall 25′ forms the acoustic member 5, thisadvantageously avoids the addition of an insert member. Preferably, theupstream face of the internal partition wall 25′ comprises a concaveportion 50′ or flat part extending substantially orthogonal to thenormal N of the ventilation opening 3 so as to form an acoustic surfacereflecting the waves entering through the ventilation opening 3. In thisway, advantage is taken of the internal partition wall 25′ to treatacoustic waves without increasing mass of the air intake 20. Preferably,the upstream face of the internal partition wall 25′ is overall convexand is locally deformed to form the concave portion 50′ with acousticsurface.

With reference to FIGS. 29 to 31, according to one aspect of theinvention, the acoustic member 5 comprises at least one absorptionmaterial 52 so as to form an acoustic absorbing surface. Preferably, theabsorbing material 52 is resistant to high temperatures, for example inthe order of 350° C., which corresponds to the order of magnitude of thetemperature of the hot air stream FAC used for de-icing.

By way of example, the absorption material 52 is of the porous, inparticular, metallic, type with or without honeycomb. Of course, othermaterials could be suitable, for example, a metal foam, ceramic materialwith a perforated skin and the like.

As illustrated in FIGS. 29 and 30, an absorption material 52 ispositioned on the acoustic surface 50 of the embodiments of FIGS. 25 and27 in order to significantly reduce acoustic nuisance. In such a case,the surface 50 is common and has only a support function, with theabsorption material 52 performing the acoustic treatment by absorption.

In this embodiment, the absorption material 52 is spaced from theventilation opening 3 along the normal axis by a spacing distance N52which is greater than the length P3 of the ventilation opening 3. Evenmore preferably, the spacing distance N52 is less than twice the lengthP3 of the ventilation opening 3. Such a compromise ensures optimal hotair exhaust as well as an optimal acoustic absorption.

With reference to FIG. 31, the internal partition wall 25 comprises aconvex upstream face pointing to the ventilation opening 3 and theabsorption material 52 is directly attached to the internal partitionwall 25 facing the ventilation opening 3. In other words, the acousticmember 5 is formed by the partition wall 25 to which the absorptionmaterial 52 is attached.

By virtue of the invention, acoustic waves are treated in a mannerinternal to the internal cavity 24, which makes it possible not toimpact the overall size of the air intake 2 as well as the external wall22. The acoustic member makes it possible to keep the acousticfrequencies away from the ranges of sensitivity of the human ear likelyto cause acoustic nuisance.

A reduction in acoustic pollution has been set forth for a singleventilation opening 3, but it goes without saying that some or all ofthe ventilation openings 3 could be associated with acoustic elements 5.When several acoustic members 5 are used together, these can beindependent or connected together, for example, continuously between twoadjacent ventilation openings 3.

Advantageously, the various aspects of the invention can be combinedwith each other for a same ventilation opening or for differentventilation openings.

Also, a disturbance, deflection or vortex generating member canadvantageously be associated with a ventilation opening 3 having anupstream edge 31 whose circumferential profile is discontinuous togenerate turbulence and/or a downstream edge 32 whose radial profile isaerodynamic to limit pressure fluctuation.

Similarly, a disturbance, deflection or vortex generating member canadvantageously be associated with an acoustic member, with or withoutabsorption material.

Similarly, an acoustic member, with or without absorption material canadvantageously be associated with a ventilation opening 3 having anupstream edge 31 whose circumferential profile is discontinuous togenerate turbulence and/or a downstream edge 32 whose radial profile isaerodynamic to limit formation of pressure fluctuations.

According to one aspect of the invention, an acoustic member, with orwithout absorption material, can advantageously be associated, in acumulative manner, with a ventilation opening 3 having an upstream edge31 whose circumferential profile is discontinuous to generate turbulenceand/or a downstream edge 32 whose radial profile is aerodynamic to limitformation of pressure fluctuations, as well as with a disturbance,deflection or vortex generating member.

1-11. (canceled)
 12. An air intake of an aircraft turbojet enginenacelle extending along an axis X in which an air stream circulates fromupstream to downstream, the air intake extending circumferentially aboutaxis X and comprising an internal wall pointing to axis X to guide aninternal air stream and an external wall which is opposite to theinternal wall, to guide an external air stream, the walls beingconnected through a leading edge and an internal partition wall so as todelimit an annular cavity, the air intake comprising means for injectingat least one hot air stream into the internal cavity and at least oneventilation opening formed in the external wall to allow exhaust of thehot air stream after heating the internal cavity, which air intakecomprises a ventilation opening comprising an upstream edge thecircumferential profile of which is discontinuous to generateturbulences and a downstream edge the radial profile of which isaerodynamic to limit formation of pressure fluctuations.
 13. The airintake according to claim 12, wherein the circumferential profile of theupstream edge has at least one point of curvature discontinuity in thevicinity of which the direction of the tangent of the profile ismodified by an angle greater than 60°, lower than 180°.
 14. The airintake according to claim 13, wherein the upstream edge comprisesbetween 1 and 8 points of curvature discontinuity for generatingturbulences.
 15. The air intake according to claim 12, wherein theupstream edge comprises at least two, at least four, turbulencegenerating patterns.
 16. The air intake according to claim 15, whereinthe turbulence generating pattern is in the form of a scallop or achevron.
 17. The air intake according to claim 12, wherein the upstreamedge is inscribed withing the aerodynamic lines of the external wall.18. The air intake according to claim 12, wherein the upstream edgecomprises an outwardly projecting portion.
 19. The air intake accordingto claim 18, wherein the projecting portion forms an angle (θ) with theoverall plane of the ventilation opening which is lower than 45°. 20.The air intake according to claim 12, wherein the downstream edge has arounded, preferably domed, radial profile.
 21. The air intake accordingto claim 12, wherein, with the ventilation opening defining anaerodynamic line as an extension of the external surface of the externalwall of the air intake, the downstream edge is positioned internally tothe aerodynamic line.
 22. The air intake according to claim 12, wherein,with the external wall comprising a through opening for assembling, theventilation opening is formed in a ventilation member mounted in,preferably from within, the through opening for assembling.